The present invention relates to a process for the selective froth-flotation of sulfidic, oxidic and salt-type minerals, whereby the ore is first wet-ground to the fineness appropriate for flotation, whereafter the obtained slurry is prepared and froth-flotated.
This invention relates in particular to the improvement of the selectivity of the flotation of sulfidic minerals in the froth-flotation process, but the process according to the invention can also be applied with success to the froth-flotation of non-sulfidic minerals such as scheelite, ilmenite, apatite and magnesite.
It is known that sulfide minerals can be froth-flotated with high selectivity by using, for example, xanthate as the collector agent; the requirement of xanthate is usually in the order of 50-500 g/t. Selectivity can be improved by using, for example, waterglass as the depressing agent for the silicates.
However, considerable difficulties are encountered in the above known process in the treatment of many sulfidic ores, especially nickel ores.
The characteristics of such problematic ores include a very high specific surface area, which can be up to 10-100 fold the specific surface area of a "healthy" ore ground to the corresponding fineness. This is usually due to the high degree of metamorphism of the ore. As a consequence of metaphorism, the particle size of the sulfide phase is often very small, and therefore the ore must be very finely ground to obtain a sufficient degree of purity of the particles. As a consequence of metamorphism the gangue, i.e. the silicate material, is also often changed. Serpentine, chlorite and talcum are very common metamorphic products in ores of this type, and owing to their softness, easy slurrying and natural hydrophobic property they tend to cause problems.
The high specific area, easy slurrying, natural hydrophobic character and flocculability of the problematic minerals, as well as the small particle size of the sulfide minerals, are the actual causes of problems. These result in, for example, and abnormally high requirement of the collector agent, about 10-fold the normal consumption mentioned previously.
The requirement of other chemicals, for example the H.sub.2 SO.sub.4 used for pH control, is also very high. In spite of the high quantities of chemicals and the high cost, the results of froth-flotation remain poorer than when using normal ore. This naturally results in a lower profitability. In many cases it is positively uneconomical to exploit ore of the said type by conventional methods.